The exact timing will not be revealed for security reasons.
Earlier on Tuesday, Mladic visited the grave of his daughter Ana, who committed suicide at the age of 23 reportedly because of accusations against her father. The retired general was taken under police guard to the Topcidersko cemetery in Belgrade and later returned to his detention cells.
The charges against Mladic include the 1995 Srebenica massacre of 8,000 Muslim men and boys and the 44-month siege of the city of Sarajevo during which 10,000 people were killed.
On Friday, a Serbian judge ruled that Mladic was fit to be transferred to The Hague. His family claim he is in extremely poor health after suffering a series of strokes and his lawyer says he does not expect him to live long enough to go to trial.
Prosecutors in The Hague are said to be looking at applying to the court to join Mladic’s trial to that of his wartime political leader Radovan Karadzic, who is facing the same charges.
Mladic’s arrest last week after 16 years on the run was widely welcomed internationally but sparked angry protests among those Serbs who think of him as a national hero.
Between 10,000 and 15,000 protesters rallied against his arrest outside parliament Sunday and 180 people were detained after skirmishes that saw far-right youth throw stones and flares at police.